1. Field of the Invention
The present invention is directed generally to engines and coolers and, more particularly, to Stirling cycle engines and coolers.
2. Description of the Related Art
A conventional Stirling cycle engine or cooler includes a displacer moved by a working fluid, such as a gas. Portions of the working fluid travel in passageways between a hot area and a cold area. As the working fluid travels from the hot area to the cold area, it passes through a conventional random fiber mesh material called a regenerator that retains heat from the working fluid thereby lowering the temperature of the working fluid. As the working fluid returns from the cold area back to the hot area, it receives some heat back from the regenerator thereby resulting in increased efficiency. Unfortunately, manufacture of conventional regenerators can demand extensive highly trained labor with many manufacturing steps.
Conventional regenerators can be difficult to integrate with other components of Stirling cycle engines or coolers, such as heat exchangers. For instance, due to differences in geometries of the conventional regenerators and heat exchangers manifolds are used to maintain uniform flow of the working fluid through the heat exchangers and regenerator. These manifolds contribute to “dead volume” that reduces efficiencies.
Another problem posed by conventional integration of regenerators with heat exchangers is that the regenerators are compressed fitted between the exchangers which adds more variableness to the final porosity of the regenerator both during time of assembly and also through the lifetime of operation. As the conventional regenerator ages, the amount of compression placed upon the regenerator by its fitting between the two heat exchangers can change, which diminishes long term reliability. In some cases compression lessens to a degree in which the regenerators become loose enough to vibrate and oscillate, which can result in shedding of small unwanted particles and subsequent machinery failure.
The random fiber mesh material used in the conventional regenerators is sintered which produces small particles that can migrate throughout the Stirling cycle engine or cooler potentially causing damage. Construction of conventional regenerators provides little in the way of accurate control over either bulk or axial regenerator porosity of the random fiber mesh material. Consequently, extensive operational testing is required to verify performance of conventional regenerators and undesirable amounts of costly scrap materials are produced. Attempted remedies include some conventional regenerators using spaced apart foils, however, spacing between these foils is undesirably inconsistent and unpredictable. Due to drawbacks of conventional regenerators and heat exchangers, reliability and performance of Stirling cycle engines and coolers suffers.